1. Field of the Invention
The invention pertains to the field of rotary joints as used with heating or cooling drums such as the dryer drums employed in the manufacture of paper.
2. Description of the Related Art
Self-supported rotary joints, as compared to trunnion mounted rotary joints, are supported by the associated rotating drum structure, and have the advantage of being relatively concise in configuration, and are easy to install and maintain. However, because self-supported rotary joints are supported by a bearing housing affixed to the rotating drum structure supporting the syphon, and prevented from rotating by the use of a torque lug, the "freezing" of a bearing within the bearing housing will cause the rotary joint nipple, which is stationary and supports the joint body head, to rotate. Rotation of the nipple will cause the joint head to rotate destroying the hose conduits attached to the head for supplying steam or water, and for removing condensate. The conduits attached to the rotary joint head are usually flexible hose reinforced with wire, and upon rotation of the joint head, the torque lug and associated anchor will be broken, the joint hoses will fracture and rotate, and the jagged edges and rotating wire will spin creating a very hazardous situation for personnel in the surrounding area. Steam will be vented to the area and until attention can be given to the situation, considerable damage can be experienced and personnel threatened.
With the advent of faster and heavier dryer drums, and larger rotary joints, it is desirable to support the rotary joint and associated nipple upon roller bearings, rather than carbon bushings. However, as roller bearings require regular lubrication and are more prone to "freezing" and seizure than carbon bushings, the use of roller bearings in self-supported rotary joints has been limited in the past compromising the desired rotary joint designs for large or high speed installations.